Annealing of gallium nitride under high-N-2 pressure

GaN is the key material for blue and ultraviolet optoelectronics. It is a s trongly bonded wurztite structure semiconductor with the direct energy gap 3.5 eV. Due to strong bonding, the diffusion processes require high tempera tures, above 1300 K. However at this temperature range at ambient pressure, GaN becomes unstable and dissociates into Ga and N-2. Therefore high press ure of N-2 is required to study the diffusion and other annealing related p rocesses. We studied annealing of bulk GaN nitride single crystals grown un der high pressure and also annealing of homo- and heteroepitaxial GaN layer s grown by MOCVD technique. Annealing at temperatures above 1300 K influenc es strongly the structural and optical properties of GaN crystals and layer s. At this temperature diffusion of the Mg and Zn accepters have been obser ved. In spite of very interesting experimental observations the understandi ng of microscopic mechanisms of these processes is limited. (C) 1999 Elsevi er Science B.V. All rights reserved.